1. Field of the Art
This invention relates to a method and an apparatus for transferring a pattern of infinitesimally minute structures in the form of dents and projections onto an energy ray-setting resin layer coated on a substrate plate, by pressing a master pattern on a pattern transfer mold against the energy beam-setting resin, and also to data storage discs and semiconductor devices with a resin layer imprinted with a pattern of minute structures.
2. Prior Art
Nano-pattern imprinting technology has been applied in various fields, for example, in the fields of electronics such as semiconductors, storage media, optical or other devices and also in the fields of information technology and biotechnology in connection with cell culture sheets. As known in the art, in nano-pattern imprinting, a pattern transfer mold, with a master pattern of infinitesimally minute structures, is pressed against a thin synthetic resin film layer coated on a substrate plate or sheet to transfer and imprint the pattern on the resin film. The transferring pattern can be a pattern of nano-structures of a linear shape or of a pillar-like shape.
Normally, a thermo-setting resin or an energy ray-setting resin is used for the synthetic resin layer to be imprinted with a nano-pattern. Of photo-setting resins typical of the energy ray-setting resins, ultraviolet curing resins such as urethane resins and epoxy resins are in wide use because of their fast-curing merit. A resin in a softened state is uniformly coated on a surface of a substrate, and a master pattern is pressed on the surface of the coated resin layer to transfer and imprint profiles of nano-structures of the master pattern, followed by irradiation of ultraviolet rays through the transfer mold or through the substrate plate to cure the imprinted resin layer. A pattern transfer mold which is made of an ultraviolet-transmitting material like quartz glass is used in a case where ultraviolet ray is irradiated through the transfer mold. Normally, a master pattern consisting of infinitesimally minute dents and projections is prepared on a transfer surface of the mold by a lithographic process.
The so-called stamping process is well known as a technology for transferring a pattern of minute dents and projections to an ultraviolet curing resin, and has been employed in the manufacture of optical discs (DVDs) and recording media in the shape of a disc. For example, as described in Japanese Laid-Open Patent Application 2002-251801, a stamper with a master pattern is set on a lower mold, face to face with a film which is supported on a transparent support body through a handling member, and an ultraviolet curing resin is fed onto the stamper and pressed the resin between the stamper and the film, followed by irradiation of ultraviolet rays to cure the pressed resin.
In this regard, a pattern can be transferred and imprinted with a satisfactory quality as long as the pattern to be transferred is low in aspect ratio, i.e., a difference in height between top and bottom, as in the case of the DVD pattern described in Japanese Laid-Open Patent Application 2002-251801. However, in nano-pattern imprinting, it is often required to transfer dents and projections which are smaller in size and higher in aspect ratio. For example, it becomes necessary to transfer a nano-pattern consisting of cylindrical or conical pillars which are several tens to several hundreds nanometers in diameter and have a high aspect ratio which is several tens times as large as the diameter. However, from the standpoint of accuracy and yield of pattern transfer, it is difficult to apply the DVD pattern transfer technology, as described in Japanese Laid-Open Patent Application 2002-251801, to transfer of nano-patterns having a higher aspect ratio.